Sn-based alloy bullet

Abstract: The invention relates to a bullet based on an Sn alloy, wherein the Sn alloy comprises Cu, Sb, Bi and/or Zn as alloying element, wherein the Sn alloy preferably contains 0.2-10% by weight Cu, preferably 0.2-6% by weight Cu, or 0.2-10% by weight Cu and 0.5-20% by weight Sb, preferably 0.2-5% by weight Cu and 0.5-10% by weight Sb, or 1-15% by weight Sb, preferably 1-10% by weight Sb, or 0.5-30% by weight Bi, preferably 5-20% by weight Bi, or 0.005-10% by weight Zn, preferably 0.01-1% by weight Zn; and to the use of an Sn alloy for manufacturing a bullet.

Description: The present invention relates to a bullet and to the use of an Sn alloy therefor.* Understood by a bullet in this context are a solid projectile and shot particles for a small-shot cartridge. At the present time lead alloys are used for bullets for sport and professional purposes. There is however increasing resistance to the use of such lead-containing bullets, since fired bullets which are not found produce in the environment ground pollution and accumulation of heavy metals in organisms due to leaching. Another problem is that when the bullet is fired the weight of the bullet decreases. This weight decrease takes the form of lead-containing dust which is inhaled during firing. Another further problem is that lead fumes are inhaled during casting of the lead-containing bullets. A lead free bullet is known from WO 92/08097. Up to the present there has been no good alternative to lead-containing bullets. A problem of other types of alloys, for instance based on iron, is that such bullets are very hard, cause damage to the barrel and, when trapped in trees, can result in damage when such trees are sawn down. A high density projectile and method of making the same is known from WO 92/22089. The invention has for its object to provide a bullet substantially free of heavy metals such as lead and cadmium, whereof both the interior ballistics (barrel fouling/dust formation) and the exterior ballistics (predictable bullet flight and accuracy) are optimal, while in terms of dimensions the bullets can be properly calibrated and have a narrow tolerance. After extensive alloy and firing tests a series of alloys has been developed which substantially fulfil the above described requirements and substantially do not have the above described drawbacks. According to the present invention there is provided a bullet based on an Sn alloy, wherein the bullet comprises 60 wt.% or more Sn. A bullet according to the present invention is substantially free of heavy metals, has good interior and exterior ballistics, can be properly calibrated and have a narrow tolerance. It has been found that bullets based on a number of Sn alloys are satisfactory, wherein Cu, Sb, Bi and/or Zn can be used as alloying element for such an Sn alloy. With respect to the alloying element Cu, the Sn alloy can contain 0.2-10% by weight Cu, preferably 0.2-6% by weight Cu. Found to suffice well in practice were Sn alloys with 1-5% by weight Cu, such as Sn 3 Cu. Such Cu-containing Sn alloys were found to have optimum interior and exterior ballistics. With regard to the alloying element Sb, both Sb-containing Sn alloys and Sb- and Cu-containing Sn alloys can be used. In the case of the combined use of Cu and Sb the Sn alloy generally contains 0.2-10% by weight Cu and 0.5-20% by weight Sb, preferably 0.2-5% by weight Cu and 0.5-10% by weight Sb. It has been found in practice that the Sn alloy preferably contains 0.5-3% by weight Cu and 0.5-8% by weight Sb. Two very interesting alloys in practice are Sn 1.5 Cu 5.5 Sb and Sn 1 Cu 3 Sb. These alloys also have optimum interior and exterior ballistic properties. If the Sn alloy contains only Sb as alloying element, Sb is generally present in a quantity of 1-15% by weight Sb, preferably 1-10% by weight Sb. Found to be very interesting in practice is an Sn alloy containing 2.5-5% by weight Sb, such as Sn 5 Sb and Sn 2.5 Sb. Another type of Sn alloys for such a bullet is based on the alloying element Bi which can be generally present in a quantity of 0.5-30% by weight Bi. Large quantities of Bi result however in an unacceptable increase in brittleness, whereby shattering of the bullet can occur. The Bi content therefore preferably amounts to 5-20% by weight. Alloys found interesting in practice are Sn alloys with 10-20% by weight Bi or 1-5% by weight Bi. Very interesting alloys are Sn 5 Bi, Sn 10 Bi, Sn 15 Bi and Sn 20 Bi. Another Sn alloy for use in a bullet according to the invention is based on the alloying element Zn. Such alloys can be cast very well and are for this reason very suitable for self-casting of bullets, for instance for "bird-shoots". Such Sn alloys generally contain 0.005-10% by weight Zn, preferably 0.01-1% by weight Zn. Found interesting in practice were Sn alloys with 0.01-0.1% by weight Zn, such as Sn 0.04 Zn. In order to further improve the ductility of the bullets according to the invention based on an Sn alloy, it is recommended to add to the Sn alloy Eutinal (90% by weight Zn, 5% by weight Al and 5% by weight Mg; see DE-A-3 135 847). For instance 0.01-1% by weight Eutinal can be added, whereby an optimum ductility is obtained. The bullets on the basis of an Sn alloy generally contain very small quantities of other alloying elements, so-called trace elements. Each trace element may be present in a quantity of less than 0.1% by weight and in total the content of trace elements amounts to less than 0.5% by weight. The bullets on the basis of an Sn alloy which contain Bi as alloying element are optimal for use in a Magnum .357 pistol wherein the bullet has outstanding interior and exterior ballistics. The bullets on the basis of an Sn alloy with Cu as alloying element are highly suitable for applications on shooting ranges. Finally, the bullets on the basis of an Sn alloy based on the alloying elements Cu and Sb are excellently suited for very many applications due to the maximal interior and exterior ballistic properties. The Sn alloy can also be usefully applied in preparation of pellets or shot in small-shot cartridges (particle size 1-5 mm, preferably 2-3 mm diameter). In the following example a large number of bullets on the basis of Sn alloys according to the invention are manufactured and firing tests were performed with such bullets using a Magnum .357. The alloys used are stated in the table below, wherein the residual weight of the bullet is also stated as a percentage of the original bullet weight. All bullets were found to possess optimum interior and exterior ballistic properties with in addition a predictable bullet flight and accuracy. The bullets were moreover found to have a hardness in the order of at least 14 Brinell, whereby shattering in a bull's eye or a shot wild animal substantially does not occur. The maximum hardness often lay below 25 Brinell, whereby penetration of bullet-proof vests and internal damage to the pistol or rifle barrel substantially do not occur. Of the alloys mentioned in the table a rough casting is made which is then calibrated to the calibre 0.357. The casting is greased and formed into a bullet by placing in a brass cartridge provided with a percussion cap and powder. Using a Magnum .357 firing tests were performed with the bullets on the basis of the diverse Sn alloys according to the invention. After each shot the fired bullet is weighed and the difference with its starting weight determined. The loss of alloy material can be seen from the residual weight as a percentage of the original bullet weight. All bullets were found to possess a good flight and accuracy and good to outstanding interior and exterior ballistic properties. The alloy Sn 0.75 Cu 0.25 Bi 0.04 Eutinal provides a finer bullet or small-shot structure whereby manufacture thereof is optimal.

Claims: Bullet based on an Sn alloy, wherein the bullet comprises 60 wt.% or more Sn. Bullet as claimed in claim 1, wherein the Sn alloy comprises Cu, Sb, Bi and/or Zn as alloying element. Bullet as claimed in claim 1 or 2, wherein the Sn alloy contains 0.2-10% by weight Cu, preferably 0.2-6% by weight Cu. Bullet as claimed in claim 3, wherein the Sn alloy contains 1-5% by weight Cu, preferably 3% by weight Cu. Bullet as claimed in claim 1 or 2, wherein the Sn alloy contains 0.2-10% by weight Cu and 0.5-20% by weight Sb, preferably 0.2-5% by weight Cu and 0.5-10% by weight Sb. Bullet as claimed in claim 5, wherein the Sn alloy contains 0.5-3% by weight Cu and 0.5-8% by weight Sb, preferably 1-1.5% by weight Cu and 1.25-5.5% by weight Sb. Bullet as claimed in claim 1 or 2, wherein the Sn alloy contains 1-15% by weight Sb, preferably 1-10% by weight Sb. Bullet as claimed in claim 7, wherein the Sn alloy contains 2.5-5% by weight Sb. Bullet as claimed in claim 1 or 2, wherein the Sn alloy contains 0.5-30% by weight Bi, preferably 5-20% by weight Bi. Bullet as claimed in claim 9, wherein the Sn alloy contains 10-20% by weight Bi. Bullet as claimed in claim 1 or 2, wherein the Sn alloy contains 0.005-10% by weight Zn, preferably 0.01-1% by weight Zn. Bullet as claimed in claim 11, wherein the Sn alloy contains 0.01-0.1% by weight Zn, preferably 0.04% by weight Zn. Bullet as claimed in claims 1-12, containing 0.01-1% by weight Eutinal. Bullet as claimed in claims 1-13, wherein the Sn alloy contains trace elements, each of which is less that 0.1% by weight and the total of which is less than 0.5% by weight. Use of an Sn alloy as claimed in claims 1-14 for manufacturing a bullet.

Inventors: BEHM HARRY, DE ROOY ROELOF, NOORDEGRAAF JAN, OUD MARTINUS ADRIANUS, BEHM, HARRY, DE ROOY, ROELOF, NOORDEGRAAF, JAN, OUD, MARTINUS ADRIANUS
Applicants: BILLITON WITMETAAL, BILLITON WITMETAAL B.V.
Application year: 1994
Main classification: F42B12
IPC codes: F42B12